The mosaic structure of red blood cell agglutinogens.

The existence of certain structures designated as agglutinogens on the red cell envelope has been inferred from the reactions, hemolysis and agglutination, which occur on contact with specific antisera. These structures, whose chemical nature is incompletely understood, are antigenic, that is, they have the capacity to stimulate the formation of immune antibodies, and the reacting substances or antibodies in the antisera are variously designated as agglutinins or hemolysins. It is now known that red cells are characterized by multiple rather than by single agglutinogens, at least one of which is species specific in that all members of a species appear to share it. Other agglutinogens are type specific and are encountered only in a certain percentage of the individuals of a species. It is with these type specific agglutinogens, the blood group antigens, that we are primarily concerned here.